1. Field of the Invention
This invention relates to a method of manufacturing a liquid discharge head which discharges liquid by applying energy from outside to the liquid.
2. Related Background Art
A liquid discharge head which discharges desired liquid by applying energy from outside to the liquid can give the desired liquid to an object of discharge without the contact by a transfer roller or the like and therefore is used for various purposes. Above all, an ink jet recording apparatus is good in printing performance and low in cost and therefore has come to be widely utilized.
In the head of the ink jet recording apparatus, as means for discharging liquid from a discharge port formed in a liquid chamber, there are various types such as a type which generates bubbles in ink by heat energy and discharges an ink droplet by a produced pressure wave, a type which attracts and discharges an ink droplet by an electrostatic force, and a type which utilizes a pressure wave by a vibrator such as a piezoelectric element. The ink jet head includes in its construction a liquid chamber which provides a pressure generating chamber, a through port which communicates with the liquid chamber and provides a discharge port, the aforedescribed discharging means, etc.
As a method of forming a flow path structure such as the liquid chamber and the through port, mention may be made of:
(1) a method of forming the liquid chamber and the through port in a substrate by a photolithographic process and laser working;
(2) a method using plastic extrusion molding using a metal mold; and
(3) a method of forming a pattern which provides a molding member for the liquid chamber and the through port, and forming resin or forming a metal by a plating process, around the molding member.
The method under item (1) above includes the step of sticking the flow path structure on other substrate on which discharging means is formed. As the sticking, mention may be made of fusion welding by the fusion by heat, pressure welding utilizing the diffusion joining by heat and load, brazing and soldering utilizing a brazing filler metal, and adhesive securing utilizing an adhesive agent. The fusion welding and the pressure welding apply heat and load and therefore, have suffered from the problem that when the device becomes high in definition and high in density, the partition wall between liquid chambers may sometimes be destroyed. Also, as regards the brazing and welding and the adhesive securing, the control of the amounts of the adhesive agent and the brazing material is very difficult, and in some cases, the leakage of the adhesive agent and the brazing material into the liquid chambers or the unsealing of the liquid chamber due to the deficiency of the adhesive agent or the brazing material has occurred.
These problems have caused a reduction in yield. Also, in the case of the adhesive agent, there has also been the problem that the pressure produced in the liquid chambers may be alleviated in some cases. Also, alignment is necessary during the welding, but there has also been the problem that this is very difficult and mass productivity lacks.
The method under item (2) above has suffered from the problem that the selection range of the plastic material is generally narrow from the condition of the mechanical characteristic thereof and the accuracy of machining and the working condition are substantially determined by the material used. Also, there has been the problem that the mechanical characteristic is low and the pressure produced in the liquid chambers is alleviated or when the produced pressure is high as in the bubble jet (BJ) type, the material may be deformed in some cases.
In the method under item (3) above, the material is low in mechanical characteristic like the plastic material, and in some cases, the alleviation of the produced pressure or the deformation by the produced pressure has occurred.
Further, as the method of forming a metal around the molding member, by the plating process the following methods can be mentioned, but each of them suffers from a problem.
In Japanese Patent Application Laid-open No. H11-115182, there is proposed a manufacturing method comprising the step of forming an integral type of nozzle and liquid chamber formed of an Ni material by electroforming, the step of forming a sacrifice layer formed of Cu in the liquid chamber, the step of forming a vibratory plate, and the step of fusing the sacrifice layer formed of Cu. In this case, it is necessary to stick the metal on a substrate on which discharging means is formed. The use of an adhesive agent during the sticking make alignment of high accuracy difficult. Also, there is a case where Cu formed as the sacrifice layer is alloyed with Ni and it becomes difficult to remove Cu only.
On the other hand, in Japanese Patent Application Laid-Open No. H08-142339 and Jae-Duk Lee, “A Thermal Inkjet Printhead with a Monolithically Fabricated Nozzle Plate and Self-Aligned Ink Feed Hole,” J. Microelectromechanical Sys., Vol. 8, No. 3, September 1999, pp. 229–236, there is mentioned a method of integrally forming a nozzle plate and side walls.
In Japanese Patent Application Laid-open No. H8-142339 (see FIG. 3A of the accompanying drawings), a molding member is formed of a first fusible resin 301 and a second fusible resin 302, whereafter an electrically conductive layer is generally formed and thereafter, metal film 304 having a predetermined film thickness is formed by electroforming, and lastly the molding member is removed to thereby form a flow path structure.
Also, in Jae-Duk Lee's publication (see FIG. 3B of the accompanying drawings), a molding member formed of a fusible resin 312 is formed on a substrate on which an electrically conductive layer 311 is formed, and metal film 313 having a predetermined film thickness is formed by electroforming, and lastly the molding member is removed to thereby form a flow path structure (Jae-Duk Lee,. “A Thermal Inkjet Printhead with a Monolithically Fabricated Nozzle Plate and Self-Aligned Ink Feed Hole,” J. Microelectromechanical Sys., Vol. 8, No. 3, September 1999, pp. 229–236).
The method of manufacturing a flow path structure disclosed by Japanese Patent Application Laid-Open No. H08-142339 and Jae-Duk Lee integrally forms a liquid chamber and a pattern providing a discharge port through which liquid is discharged from the liquid chamber with a fusible resin, and thereafter forms a plating layer around the pattern to thereby form a flow path structure. The liquid chamber can be formed directly on a substrate and therefore, the step of sticking is not included.
As a result, the problem due to sticking is solved, but in the case of Japanese Patent Application Laid-Open No. H08-142339, if the plating seed layer formed on the pattern is formed on the wall surface of the pattern providing the discharge port, the discharge port is closed by the plating layer and therefore, it becomes necessary to manufacture the flow path structure so that the plating seed layer may not be formed on at least the wall surface of the pattern providing the discharge port.
Methods of forming anisotropic metal film include a vapor depositing method, a sputtering method, etc., but to prevent a plating seed layer from growing on a side of a pattern, the pattern providing a discharge port need be of at least a taperless shape (the areas of the upper surface and lower surface of a molding member of a second fusible resin are equal to each other), and more preferably be of an inverted tapered shape (the area of the lower surface of the molding member of the second fusible resin is smaller than that of the upper surface thereof).
If the pattern providing a discharge port is made into an inverted tapered shape, there will arise the problem that the shape of the discharge port formed in the liquid chamber also becomes an inverted tapered shape and the deposition accuracy of the discharged liquid becomes lower than when the sticking method is used.
Also, in the case of Jae-Duk Lee's publication, the liquid chamber and the pattern providing a discharge port through which the liquid is discharged from the liquid chamber are integrally formed of a fusible resin, whereafter plating is grown from the seed layer of the plating formed on a substrate, and this leads to the problem that the corners of the cross-sectional shape of the discharge port becomes rounded and the deposition accuracy becomes lower than when the sticking method is used.